By applying a driving voltage to drive thin film transistor (TFT) in pixel unit is wildly used in various display devices. Amorphous silicon (a-Si) material with good stability and process ability has been used as a material of the active layer of the TFT for a long time. However, the lower carrier mobility of a-Si material cannot meet the requests for large-size and high-resolution display panels.
Based on high mobility of poly-silicon, a high-speed complementary metal oxide semiconductor (CMOS) driving system can be made directly on a substrate by adopting low-temperature polysilicon (LIPS) technology. Such that, the number of pins of an external printed circuit and the bonding points of wires are few, making the display panel fewer defects, improving the reliability of the product and increasing the durability. Compared to amorphous silicon (a-Si) thin film transistors, low-temperature polysilicon thin film transistors have more excellent physical electrical properties, such as smaller components, which can improve the light transmittance, thereby reducing the backlight load and prolonging the life of the liquid crystal display panel. Therefore, LTPS technology is widely used in the LCD industry. However, in the production of LTPS-TFT process, the production process temperature is up to 600° C., metals with relative low melting point cannot be used herein. In addition, due to the market demand for high-performance large-size panels, in the production process of the large-size panels, increasing panel size will increase the length of gate metal wires. The wiring trace becomes too long, and a corresponding resistance is increased. Such that the loading of the gate is too large, the screen uniformity of the panel cannot be guaranteed. If thicken the gate metal film layer directly, substrate fragmentation will be generated due to large stress, the actual purpose of production becomes meaningless. Therefore, metals with relative low resistivity are needed, aluminum and other metals having low melting point and low resistivity cannot be used, thus in the current process, molybdenum is used for the gate wire.